Great thread.
Loved some of these movies. To get down to 4...that's tough.
"Death of Stalin" is great but its humor is not as important as it tackling the subject matter. Very similar to "Doctor Strangelove" in that regard.
all of the Monty Python movies are great and I love all the humorous movies that Terry Gilliam did since (e.g., "The Fisher King", "Twelve Monkeys").
My American Mount Rushmore of Comedy: I'm going to have to work hard to narrow this down to 4.
"This is Spinal Tap" The police said it was a crime best left, unsolved really - Rob Reiner comedy tree
"Galaxy Quest" We've got to get out of her before one of those things kills Guy!
"Tommy Boy"
"The Big Lebowski"
"Office Space"
"Stripes"
"Animal House" and "Vacation" both from National Lampoon
"The Blues Brothers"
"Zoolander"
"Spy"
My British Trafalgar Square of Comedy
"In Bruges"
The Corneto Trilogy: "Hot Fuzz," "Shaun of the Dead," "At the End of the World"
All the Monty Python movies: "Holy Grail" being leader of the pack